Immigrants in California live longer than the state's U.S.-born residents, according to a study released today by the Public Policy Institute of California.

Immigrants have a life expectancy of more than 81 years, on average, compared to 77 years for Californians born in the United States, according to the study, which used data from the U.S. Census and the state Department of Health Services.

"When people hear that, they're surprised," said Hans Johnson, the lead author of the report, "because immigrants tend to have lower socio-economic status, less access to health care and often come from countries that have high mortality rates."

Johnson speculated that immigrants may be living longer because they have healthier diets and are less likely to smoke. He added that a kind of self-selection may also contribute to the results.

Bay Area health professionals who work with immigrants said their clientele may live somewhat healthier lifestyles, but they still face obstacles to good health.

"If immigrants had better access to health care here, that life span would be even greater than what it is," said Kent Woo, director of NICOS, a coalition of groups providing health care in San Francisco's Chinese community. "We found a lot of people tend not to take advantage of preventive care like cancer screenings. For example, Chinese women get breast exams and pap smears at about half the rate of white women. The same with prostate exams for men."

Interesting note: many descendents of immigrants from harsher environments (deserts, etc.) are at an increased risk of acquiring type II diabetes. There is some debate as to whether it is due to a 'thrifty phenotype vs thrifty genotype" selection (read: if your body is used to digesting foods that thrive in the desert, which tend to be harder to digest, and you eat foods that are easy to digest (i.e., McDonalds), then your body is almost too "efficient" at digesting the foods.

The result: insulin resistance, pre-diabetic state, and finally, diabetes. An example of this is the Pima indians of the US southwest. It is also becoming increasingly common amongst the 2nd and 3rd generations of certain groups of Asians.

A similar effect can be seen in extremely low birthweight premature infants.